1. Field of the Invention
This invention relates to an improved hermetically sealed container capable of withstanding elevated pressures and to a process for making the container and process which is especially adapted for use as an all plastic seltzer syphon package and for providing such an all plastic seltzer syphon package. Most especially, the invention relates to such a package incorporating an improved hermetic seal and to a process for making the hermetic seal.
2. Description of the Prior Art
The extensive prior art pertaining to syphon seltzer water packages has been set forth in the first related application listed above. Briefly, until the inventions of the first three related applications, seltzer water was conventionally packaged in thick glass bottles with permanently attached heads. The bottles were filled through the heads, shipped to the consumer, used by the consumer and returned to the bottler for cleaning and refilling, all without removing the head from the bottle. In order to dispense the seltzer water through a syphon, pressures of at least about 90 pounds per square inch are required, substantially higher than for conventional carbonated beverages, and may reach 125 p.s.i. Glass containers filled to such pressures are dangerous. This fact and the economics of the distribution process resulted in a decline in the syphon seltzer water business to the point that syphon seltzer water is available in only a few areas of the United States at the present time.
The inventions of the above related applications have, for the first time, made it practical to package syphon seltzer water in plastic bottles with the dispensing head separated from the bottles. The packages disclosed in the first three and the last related applications include a normally closed valve in the neck of the containers. The bottles may be shipped in conventional distribution channels with twist-off caps, which the consumer removes and replaces with a reusable dispensing head which is used to open the valve in order to dispense the seltzer water from the package. Unlike conventional carbonated beverage containers, these packages and the higher pressures employed allow the seltzer water to remain pressurized until the container is emptied, so that the product does not go flat when the container is partly empty.
As taught in these applicatios, it is desirable to provide the normally closed valve in an insert which is ultrasonically bonded to the neck of the package container. A variety of ultlrasonic bonding processes are also known in the art. The following issued U.S. patents relate generally to the ultrasonic bonding of plastics: U.S. Pat. No. 3,728,184, issued Apr. 17, 1973 to Burke et al.; U.S. Pat. No. 3,783,061, issued Jan. 1, 1974 to Hahn; U.S. Pat. No. 3,947,307, issued Mar. 30, 1976 to Buchscheidt; U.S. Pat. No. 4,140,058, issued Feb. 20, 1979 to Ballreich et al.; U.S. Pat. No. 4,356,926, issued Nov. 2, 1982 to Priestly et al. U.S. Pat. Nos. 3,563,822, issued Feb. 16, 1971 to Fesh and 4,088,257, issued May 9, 1978 to Devine disclose tack or spot ultlrasonic welding of plastics. U.S. Pat. No. 4,411,783, issued Oct. 25, 1983 to Dickens et al. teaches that ultrasonic fluid tight seals should include double or triple shear seals in order to withstand elevated pressures.
The following additional references relate specifically to the ultrasonic bonding of polyethylene terephthalate (PET): Japanese Patent Publication 54062260, dated May 19, 1979; West German Published Application 1779457, dated Sept. 23, 1971; Japanese Patent Publication 57088427, dated June 2, 1982. While it is apparent that the art pertaining to ultrasonic welding and beverage containers is well developed, problems have been encountered in applying prior art ultrasonic welding techniques to the formation of all PE hermetically sealed beverage containers capable of withstanding elevated pressures of up to at least about 90 p.s.i. required for seltzer syphon packages.